I have a subdomain where I have the catch-all enabled so I can create emails on the fly. Yes, I get a bunch of spam there as a side-effect. I can deal with it on the most part, but lately, I’ve been getting a bunch of spam with the subject of “Software”. Just that one word. I’d like to filter that out, but putting that in the Keyword spam filter would also catch anything that has “software” AND other words too, wouldn’t it??? Is there a way with either the Keyword spam filter, or the SpamAssassin mailbox filters to auto-delete based on an “exact” subject match???

I don’t know the answer to your question about further tuning your spam filter, but I did want to share something with you that might help in general.

As you pointed out, catch-all email setups are a major spam catcher. You indicated that you chose to “suffer” this “side effect” consequence in order to be able to “create emails on the fly”, so I’m wondering if you know about DreamHost’s support for “plus-addressing”?

Introduced a little over a year ago, this feature allows you to create addresses as you need them without having to use a catch-all.

I think we’ve already had more than our fair share of totally awesome
features for the month of September, plus three days, but I’ve been
wrong once before (I’m sure of it).

Which is why it never hurts to add a few more not-your-run-of-the-mill
features. Say for example, this one… a feature I’m pretty darn sure NO
OTHER WEBHOST ON THE PLANET OFFERS. And I say this after literally years
of checking:

Starting right now, all your email addresses have a sneaky new feature:

Built-in catchalls!

How does it work? It’s easy! For every email address we host you can add
a + sign and then ANYTHING before the @, and it’ll go to the same place.

I’m familiar with using the + addressing, but while Dreamhost supports it, some other sites don’t. For example, I attempted to register for a govt. site for work recently using a plus address (our work website and email is also on a DH hosted domain) and they refused to accept the + formatted email as a valid address. Only after I removed the + would they accept it as valid.

And, like the other poster here, I too have a TON of addresses now on my subdomain that rarely get mail, but I wouldn’t want to shut off by shutting down the catch-all, but i don’t have a record of them all, so I couldn’t explicitly create them.

And then when they start spamming you some day, you can easily set up your mailbox to auto-delete messages sent to that address! …how is this done? do i set up a forwarding address for me+whatever to delete everything, or is this something different?

You know, I never have tried to do that, so I’m really not sure (I use POP, and I just flag one of them as spam, and Thunderbird’s filter grabs it from that point on).

Yes, I’ve also found that to be true. It seems that many sites’ validation routines don’t recognize an email address with a " " sign in it as being a valid email address.

In that case if its really important you can always set up an additional address and set it to forward to the whichever email address when you set it up, maybe a bit more work but achieves the same thing.